The fire extinguishment of a mixture of lithium-ion cathode and electrolyte is investigated based on the use of flame retardants. Four boehmite-based flame-retardants are embedded in the LiFePO4 cathode including 0.95 mu m AIOOH-L, 0.35 mu m AIOOH-S, and their individual microcapsules. The microcapsules are denoted as en-A100H-L and en-A100H-S. Here, the shell material is the chemically stable poly(ureaformaldehyde). The rheology of the cathode slurries improves as flame-retardants are added. This is especially significant for cases using microencapsulated boehmites, en-AIOOH-L and en-AIOOH-S. At 5-15 wt%, the smaller AIOOH-S and en-AIOOH-S exhibit much better fire-extinguishing efficiency values-40-50% versus 30-40% for the larger A100H-L and en-A100H-L. This is because the smaller powder can be easier to form a dense barrier against further decomposition of the combustible materials. Among the four retardants, en-A100H-S is the best. It shows good fire retardancy in the cathode electrolyte mixture without significant electrochemical sacrifice of the cathode. (C) 2017 Elsevier Ltd. All rights reserved.